In recent year, a demand for printers has been increased accompanying the diffusion of personal computers into homes. In particular, ink-jet printers have significantly been diffused because of their small noise during operation, the capability of high-speed printing, and the ease of application for color printing.
Heretofore, various systems of ink-jet printers have been proposed.
FIG. 13 is a sectional view showing the construction of a conventional head for a pressure control type ink-jet printer. As FIG. 13 shows, such a head has the construction in which ink 56 stored in an ink chamber is ejected for printing through a nozzle opening 53 of a nozzle-forming film 51 dropwise using an ultrasonic oscillator 58 according to pulse signals.
Next, FIG. 14 is a sectional view showing the construction of a conventional head for a heater heating type ink-jet printer. As FIG. 14 shows, such a head has the construction in which ink 56 is heated according to pulse signals by a heater 55 to which electrodes 54 are connected to produce air bubbles 57 and eject the ink 56 through a nozzle opening 53 of a nozzle-forming film 51.
In both systems, a film having a thickness between 0.1 and 0.5 mm consisting of polyimide which excels in heat resistance is used as the nozzle-forming film 51. Since the nozzle opening 53 of the nozzle-forming film 51 is often formed by a laser heating process, and heat resistance is required for the film, polyimide is usually used as the material for the nozzle-forming film 51.
Next, FIG. 15 is a sectional view showing ink ejection in a conventional ink-jet printer. When ink 56 is ejected through a nozzle opening 53, it is essential for high-quality printing that the ink 56 is ejected straight as FIG. 15(a) shows.
However, conventional ink-jet printers have a drawback in that if the ink 56 conforms to the nozzle-forming film 51 and wets the film 51, the ink 56 is attracted toward the wet surface resulting in that the ink 56 cannot be ejected straight as FIG. 15(b) shows, and the track of ink ejection becomes unstable. There was a problem that, in particular, if the ink is ejected for a long period of time, the nozzle forming film 51 tended to be wet by the ink and thus the quality of printing was degraded.